ABSTRACT
The purpose of this chapter is to provide a review of the types of lipids found in muscle and adipose tissue, along with structural features and their locations. Muscle becomes food once harvested from the animal as meat, and contains numerous nutrients that originated as complex chemical components that functioned in supporting the contractile nature of the organ. Intra-and extracellular water occupies most of the mass characteristics of fresh meat, followed by protein. Contractile protein, along with lesser concentrations of bioactive proteins and peptides, provide for the protein of meat. However, connective tissue of several varieties must not be ignored. Collagen, for example, exists in numerous forms designed to function in support processes, including the matrix that houses adipocytes, which within a particular depot constitutes adipose tissue. Within muscle of meat animals, adipose tissue can exist and is commonly referred to as marbling fat (composed of interfascicular adipocytes). Intramuscular lipid would then consist of lipid of muscle cell membranes, any intramuscular triacylglycerols, and the lipid of marbling fat. Thus, muscle can include varying concentrations of lipid based on the level of marbling of that particular muscle. Meat from muscle essentially devoid of marbling will contain a small proportion of total mass as lipid, usually about 1.0%; whereas meat that contains visible marbling will contain up to about 3% to 4% lipid, with ranges of 2.6% to 15.7% reported in early work by Link and co-workers (1970). The lipid contained within muscle without marbling adipose tissue functions primarily as muscle cell membranes and constitutes most of the polar or phospholipids (glycerophospholipids); concentrations of these lipids are nearly constant during growth and deposition of marbling fat. Thus, lipids associated with the muscle cell provide for structure of the organ by supporting membrane morphology and integrity. Lipids contained within the adipocytes of marbling and the other fat depots primarily function in
13.1 Introduction .......................................................................................................................... 247 13.2 Types and Structural Characteristics of Muscle-Associated Lipids .....................................248
